(A) Field of the Invention
The present invention relates to a method for fabricating group III (Al, Ga, and In)-Nitride thin films to build and also protect electronic devices. Particularly, this invention discloses a method for fabricating thin films of AlN, GaN, InN, and Al—Ga—In multicomponent nitride alloy on sapphire and glass by electron beam evaporation technique and demonstrate a method for applying the thin film coating technique to protect solar cell against space radiation and atmospheric induced degradation.
(B) Description of the Related Art
Group III-nitride system such as AlN, GaN, InN, and their alloys such as Al(1-x)GaxN, In(1-x)GaxN, Al(1-x)InxN are widely used in the semiconductor industry in a variety of applications because of its wide and tunable band gap, high thermal conductance, piezoelectric qualities, and radiation hardness [references 0035-0062]. The thermal stability and doping capabilities make this system very useful for UV, blue and green LED and Laser Diodes, visible blind UV photo detectors, rf electronics and high temperature and high power electronics. The current technologies used in producing AlN, GaN, and InN thin films and their alloys are Metal Organic Chemical Vapor Deposition (MOCVD), Hydride Vapor Phase Epitaxy (HVP), Molecular Beam Epitaxy (MBE), and Pulsed Laser Deposition (PLD) techniques. There is only one report that presents deposition of AlN thin film using electron beam deposition [0062]. This paper reports fabrication of AlN thin film for silicon-on-insulator (SOI) application. It does not report or represent any advancement of their method towards fabrication of optical coatings and crystalline AlN, GaN, Al—Ga—In—N alloy films that are needed for electronic and/or optoelectronic device applications and their applications for radiation hard electronics.
Due to large band gaps of AlN (6.2 eV) and GaN (3.4 eV) and their alloys (Al(1-x)GaxN with band gap ranging from 3.4 eV to 6.2 eV as a function of composition) coatings and thin films of group III-nitride material system are useful for optically transparent window in the visible range of optical spectrum for electronic devices such as solar cells, detectors, uv-visible, infrared cameras, lasers and their surface protection against any environment. For example, cover glasses made from SiO2 manufactured by a number of purveyors are currently used to shield solar cells from atmospheric degradation and damaging space radiation (for solar cell operating in space). Particularly, for space application, the effectiveness of cover glasses is, however, limited and leads to solar life limitations or weight penalties which are undesirable.
This patent discloses a method of fabrication of III-Nitride system using electron beam evaporation technique in reactive atmosphere created by e-beam evaporated metal and reactive ammonia (NH3) and use of such coatings and buffer layers for fabrication of optoelectronic, electronic devices, radiation hard electronics, high-temperature and high power electronics, with emphasis on method for fabricating cover for device protection.